The United States took the rare step on Monday of formally labeling China a currency manipulator, as trade relations between the two countries continued to spiral downward after President Donald Trump’s decision last week to impose additional tariffs on Chinese goods.

“In recent days, China has taken concrete steps to devalue its currency, while maintaining substantial foreign exchange reserves despite active use of such tools in the past,” the Treasury Department said in a statement that followed the People’s Bank of China’s decision to let its currency, the renminbi, fall to the lowest level in more than a decade.